TWI438839B - Passivation layer formation by plasma clean process to reduce native oxide growth - Google Patents

Description

Method for forming a passivation layer by plasma cleaning treatment to reduce growth of native oxide

Embodiments of the present invention generally relate to methods for treating substrates, and in particular to methods of oxide etching during a plasma cleaning process.

In the manufacture of semiconductors, displays, solar cells, and other electronic devices, native oxides are typically formed when the surface of the substrate is exposed to oxygen and water in the air. Oxygen exposure occurs when the substrate is moved between a plurality of process chambers under atmospheric or ambient conditions, or when a small amount of oxygen is retained in the process chamber. Primary oxides can also be caused by contamination during the etching process. Primary oxide films are usually very thin, for example between 5-20 Between, but thick enough to cause difficulties in the subsequent manufacturing process. Therefore, the native oxide layer is often not appreciated and needs to be removed prior to subsequent manufacturing processes.

Such difficulties often affect the electrical properties of the electronic components formed on the substrate. For example, a particular problem arises when a native yttria film is formed on an exposed ruthenium containing layer, especially during the processing of a metal oxide 矽 field effect transistor ("MOSFET") structure. The hafnium oxide film is electrically insulating and is not expected to be at the interface with the contact electrode or the interconnected electrical path because the hafnium oxide film causes high electrical contact resistance. In the MOSFET structure, the electrode and interconnect paths comprise a metal telluride layer formed by depositing a refractory metal on the bare ridge and annealing the layer to produce a metal mash layer. The native ruthenium oxide film at the interface between the substrate and the metal reduces the compositional uniformity of the metal telluride layer by hindering the diffusion chemical reaction for forming the metal ruthenium. This can result in low substrate yield and high failure rate due to overheating at the electrical contacts. The native ruthenium oxide film also hinders the attachment of other CVD or sputtered layers that are subsequently deposited on the substrate.

Sputter etching processes have been used to reduce contaminants in large or small features with aspect ratios less than about 4:1. However, the sputter etch process can damage the delicate ruthenium layer by physical bombardment. In this regard, a wet etching process using hydrofluoric acid has also been used to remove native oxides. However, the wet cleaning etch process is disadvantageous for components having an aspect ratio of more than 4:1 and especially a smaller aspect ratio of more than 10:1. In particular, aqueous solutions have the difficulty of penetrating into vias, joints, or other small features formed in the surface of the substrate. Therefore, the removal of the native oxide film is not complete. Likewise, if the etch solution successfully penetrates the small features, once the etch is complete, the wet etch solution is more difficult to remove from the features. In addition, wet etching processes typically have tight timing control, can create undesirable water marks on the substrate, and have environmental considerations due to the large amount of toxic waste water.

Another way to remove the native oxide film is a dry etch process, such as a dry etch process using fluorine (F ₂ ) gas. However, the absence of a fluorine-containing gas, that is, fluorine, typically remains on the surface of the substrate. Fluorine or fluorine groups remaining on the surface of the substrate are detrimental. For example, residual fluorine atoms continue to etch the substrate to form pores within the substrate.

A more recent way to remove native oxide has formed a fluorine/barium containing salt on the surface of the substrate which is subsequently removed by a thermal annealing process. In this manner, a thin salt layer is formed by reacting a fluorine-containing gas with a surface of cerium oxide. The salt is then heated to a temperature sufficient to decompose the salt into volatile by-products, which are subsequently removed from the process chamber, and the formation of the reactive fluorine-containing gas is typically by thermal addition or by plasma energy. To assist. Salts are typically formed at low temperatures where it is desirable to cool the surface of the substrate. This cooling followed by heating is carried out by transferring the substrate from a cooling chamber where the substrate is cooled to a separate annealing chamber or furnace where the substrate is heated. Achieved.

This reactive fluorine process sequence is unpleasant for a variety of reasons. That is, since it involves the time of substrate transfer, the productivity is greatly reduced. Furthermore, during the transfer of the substrate between the plurality of chambers, the substrate is extremely susceptible to further oxidation or other contamination. Furthermore, the need for two separate chambers to complete the oxide removal process doubles the cost.

Therefore, a need exists for a method to remove or etch native oxide while passivating the underlying substrate surface, preferably within a single process chamber.

The embodiments described herein provide a method for removing native oxide on a substrate while passivating the underlying substrate surface. In one embodiment, the present invention provides a method for removing native oxide from a surface of a substrate, comprising: placing a substrate in a process chamber, the substrate containing an oxide on the surface of the substrate a layer; adjusting a first temperature of the substrate to about 80 ° C or less; generating a cleaning plasma from a gas mixture in the process chamber, wherein the gas mixture comprises ammonia and nitrogen trifluoride and NH ₃ /NF _{The 3} molar ratio is about 10 or greater; and during a plasma cleaning process, the cleaning plasma is condensed onto the substrate and a film is formed. The film comprises ammonium hexafluoroantimonate partially formed from the ruthenium of the native ruthenium oxide layer. The method further includes heating the substrate to a second temperature of about 100 ° C or greater in the process chamber while removing the film from the substrate and forming a passivated surface on the substrate. In one example, the first temperature of the substrate is between about 20 ° C and about 80 ° C, and the second temperature of the substrate is between about 100 ° C to about 200 ° C. In another example, the first temperature of the substrate is between about 22 ° C and about 40 ° C and the second temperature of the substrate is between about 110 ° C to about 150 ° C.

In another embodiment, a method for removing native oxide from a surface of a substrate is provided herein, comprising: placing a substrate in a process chamber, the substrate comprising an oxide layer on a surface of the substrate Adjusting a first temperature of the substrate to less than about 100 ° C; producing a cleaning plasma from a gas mixture within the processing chamber. The gas mixture comprises ammonia and nitrogen trifluoride and NH ₃ / NF ₃ mole ratio of about 20 or greater, and the plasma cleaning system to a RF power between about 5 watts to about 50 watts to produce. The method further includes exposing the substrate to the cleaning plasma during a plasma cleaning process to form a film comprising ammonium hexafluoroantimonate. The method further includes heating the substrate to a second temperature of about 100 ° C or greater in the process chamber while removing the film from the substrate and forming a passivated surface on the substrate.

In another embodiment, a method for removing native oxide from a surface of a substrate is provided herein, comprising: placing a substrate in a process chamber, the substrate comprising an oxide layer on a surface of the substrate Adjusting a first temperature of the substrate to less than about 100 ° C; producing a cleaning plasma from a gas mixture within the processing chamber. The gas mixture comprises ammonia and nitrogen trifluoride and NH ₃ / NF ₃ mole ratio of about 10 or more, and the plasma cleaning system to a RF power between about 5 watts to about 50 watts to produce. The method further includes: exposing the substrate to the cleaning plasma to form a film during a plasma cleaning process, wherein the film comprises ammonium hexafluoroantimonate partially formed from a ruthenium oxide layer; in the process chamber Heating the substrate to a second temperature of about 100 ° C or greater while removing the film from the substrate and forming a passivated surface on the substrate; and growing an epitaxial layer on the passivated surface of the substrate .

Embodiments of the present invention provide that the NH ₃ /NF ₃ molar ratio can be about 10, about 15, about 20 or greater, while the cleaning plasma is between about 5 watts and about 50 watts (preferably RF power is generated from about 15 watts to about 30 watts. The gas mixture is formed by flowing ammonia and nitrogen trifluoride into and into the process chamber. The flow rate of ammonia can be between about 20 sccm and about 300 sccm, preferably between about 40 sccm and about 200 sccm, more preferably between about 60 sccm and about 150 sccm, and more preferably between about 75 sccm and about. Between 100sccm. The flow rate of the nitrogen trifluoride may be between about 1 sccm and about 60 sccm, preferably between about 2 sccm and about 50 sccm, more preferably between about 3 sccm and about 25 sccm, and more preferably between about 5sccm to about 15sccm.

The passivated surface limits further formation of additional native oxide growth on the substrate upon subsequent exposure to ambient conditions outside the process chamber. For example, in an external environment, a subsequent native oxide layer can be formed to have about 6 between about 5 hours and about 25 hours. Or smaller thickness. In another embodiment, in an external environment, the subsequent native oxide layer can be formed to have about 8 during a period of between about 15 hours and about 30 hours. Or smaller thickness. In another embodiment, an epitaxial layer can be grown on the passivated surface of the substrate after the native oxide layer is removed.

Figure 1 shows a partial perspective view of a substrate 10 having a shallow trench isolation region formed therein. The substrate 10 shown in the figures is only partially fabricated and has shallow trenches 2 formed in the ruthenium layer 1. The enamel layer 1 may be a sub-layer containing or may be a sub-substrate. The shallow trench 2 is filled with oxide and is used to isolate built-in electronic components (in this case, transistors). The source 3 and the drain 4 can be formed in the shallow trench 2 by implanting ions therein. The polysilicon 5 is disposed between the source 3 and the drain 4, and the gate oxide layer 6 is disposed between the germanium layer 1 and the polysilicon 5.

Figure 2 shows a partial cross-sectional view of the substrate 10 along the tangent 2-2. Figure 2 shows where the polysilicon 5 contacts the shallow trench 2. The shallow trench 2 is formed via the thermal oxide layer 7 and the deposited oxide layer 8. The pre-polysilicon etch/clean step is performed by a wet etch process using HF. Since the HF etches the thermal oxide layer 7 faster than the etch-deposited oxide layer 8, the gap 9 is formed in the shallow trench 2. Subsequent polysilicon deposition causes the polysilicon 5 to fill the gap 9 and coat the source 3 or the drain 4, causing parasitic bonding or leakage current.

Figure 3 shows a cross-sectional view of process chamber 100 in accordance with an embodiment of the present invention. In this embodiment, the process chamber 100 includes a lid assembly 200 disposed at an upper end of the chamber body 112, and a support assembly 300 disposed at least partially within the chamber body 112. The process chamber also includes a distal plasma generator 140 having a U-shaped cross-section distal electrode. Preferably, the process chamber 100 and associated hardware are formed from one or more process compatible materials such as aluminum, anodized aluminum, nickel plated aluminum, nickel plated aluminum 6061-T6, stainless steel, and The foregoing combinations and alloys thereof.

The support assembly 300 is partially disposed in the chamber body 112. The support assembly 300 is raised and lowered by a shaft 314 that is surrounded by a bellows 333. The chamber body 112 includes a slit valve opening 160 formed in a sidewall thereof to provide access to the interior of the process chamber 100. The slit valve opening 160 is selectively opened and closed to allow a substrate processing robotic arm (not shown) to access the interior of the chamber body 112. In one embodiment, the substrate can be transported through the slit valve opening 160 into and out of the process chamber 100 to an adjacent transfer chamber and/or load lock chamber (not shown), or other chamber within the cluster tool. Exemplary clustering tools include, but are not limited to, available from Applied Materials, Inc. of Santa Clara, California. , , with platform.

The chamber body 112 also includes a channel 113 formed therein for circulating a heat transfer fluid therein. The heat transfer fluid can be a heating fluid or a coolant and is used to control the temperature of the chamber body 112 during processing and substrate transfer. The temperature of the chamber body 112 is important to prevent undesired condensation of gases or by-products on the walls of the chamber. Exemplary heat transfer fluids include water, ethylene glycol, or mixtures thereof. Exemplary heat transfer fluids can also include nitrogen.

The chamber body 112 further includes a liner 133 that surrounds the support assembly 300 and is removable for maintenance and cleaning. The inner liner 133 is preferably made of a metal or ceramic material such as aluminum. However, compatible materials can be used during the process. To increase the adhesion of any material deposited on the liner 133, the liner 133 can be grit blasted, thereby avoiding material spalling that causes contamination of the process chamber 100. Liner 133 typically includes one or more apertures 135 and a pumping passage 129 formed therein (which is in fluid communication with a vacuum system). The bore 135 provides a flow path for gas to enter the pumping passage 129, while the pumping passage provides a flow path through the liner 133 so that gas can exit the process chamber 100.

The vacuum system can include a vacuum pump 125 and a throttle valve 127 for regulating gas flow within the process chamber 100. The vacuum pump 125 is connected to a vacuum crucible 131 disposed on the chamber body 112 and is in fluid communication with a pumping passage 129 formed in the liner 133. To regulate the flow of gas within the process chamber 100, the vacuum pump 125 and the chamber body 112 can be selectively isolated by a throttle valve 127. The terms "gas" and "multiple gases" are used interchangeably unless otherwise indicated, and refer to one or more precursors, reactants, catalysts, carriers, purges, cleaning, combinations thereof, and any introduction chambers. Other fluids within the body 112.

The lid assembly 200 includes a plurality of components stacked together. For example, the lid assembly 200 includes a lid edge 210, a gas delivery assembly 220, and a top plate 250. The cover rim 210 is designed to support the weight of the various components that make up the lid assembly 200 and is coupled to the upper surface of the chamber body 112 to provide access to the interior chamber components. The gas delivery assembly 220 is coupled to the upper surface of the cover rim 210 and is arranged to minimize thermal contact with the cover rim. The components of the lid assembly 200 are preferably made of a material having high thermal conductivity and low thermal resistance, such as an aluminum alloy having a high smoothness surface. The thermal resistance of the component is preferably less than about 5 x 10 ^-4 m ² K/W.

Gas delivery assembly 220 can include a gas distribution plate 225 or a showerhead. One or more gases are typically supplied to the process chamber 100 using a gas supply panel (not shown). A particular gas or gases are used depending on the process to be performed within the process chamber 100. For example, typical gases include one or more precursors, reducing agents, catalysts, supports, purification, cleaning, or mixtures or combinations thereof. Typically, one or more gases introduced into the process chamber 100 are introduced into the lid assembly 200 and then enter the chamber body 112 via the gas delivery assembly 220. An electronically operated valve and/or flow control mechanism (not shown) can be used to control the flow of gas from the gas supply to the process chamber 100.

In one aspect, gas is delivered from the gas supply panel to the process chamber 100, wherein the gas line is split into two separate gas lines that provide gas to the chamber body 112 as described above. Depending on the process, any number of gases can be delivered in this manner and can be mixed in the process chamber 100 or prior to being transferred to the process chamber 100.

Still referring to FIG. 3, the lid assembly 200 can further include an electrode 240 for generating a plasma of the reactive species within the lid assembly 200. In this embodiment, the electrode 240 is supported on the top plate 250 and is electrically isolated therefrom. A spacer fill ring (not shown) is disposed around the bottom of the electrode 240 to separate the electrode 240 from the top plate 250. An annular spacer (not shown) is disposed around the upper portion of the spacer filling ring and is seated on the upper surface of the top plate 250 as shown in FIG. An annular spacer (not shown) is then placed adjacent the upper portion of electrode 240 to electrically isolate electrode 240 from other components of cover assembly 200. Each of these rings, the spacer fill ring and the annular spacer may be made of alumina or any other electrically insulating material compatible with the process.

The electrode 240 is coupled to a power source 340 while the gas delivery assembly 220 is grounded. Thus, plasma of one or more process gases can ignite within the space formed between electrode 240 and gas delivery assembly 220. The plasma can also be contained in the space formed by the partition. In the absence of a zone separator assembly, the plasma is ignited and contained between the electrode 240 and the gas delivery assembly 220. In either embodiment, the plasma can be well confined or housed within the lid assembly 200.

Any power source capable of activating the gas into a reactive species and maintaining the plasma of the reactive species can be used. For example, radio frequency (RF), direct current (DC), alternating current (AC), or microwave (MW) based power discharge techniques can be used. Activation can also be produced by thermal based techniques, gas collapse techniques, high intensity light sources (eg, UV energy), or exposure to x-ray sources. Alternatively, a remote activation source, such as a remote plasma generator, can be used to generate a plasma that will subsequently be delivered to the reactive species in the process chamber 100. Exemplary distal plasma generators are available from vendors such as MKS Instruments, Inc. and Advanced Energy Industries, Inc. Preferably, the RF power source is coupled to the electrode 240.

Gas delivery assembly 220 may be heated depending on process gases and operations to be performed within process chamber 100. In an embodiment, a heating member 270, such as a resistive heater, is coupled to the gas delivery assembly 220. In an embodiment, the heating member 270 is a tubular member and is embedded in the upper surface of the gas delivery assembly 220. The upper surface of the gas delivery assembly 220 includes a groove or recessed passage having a width that is slightly smaller than the outer diameter of the heating member 270 to retain the heating member 270 in the groove using an interference fit.

Since each component of the delivery assembly 220 (including the gas delivery assembly 220 and the compartment component 230) is electrically coupled to one another, the heating member 270 can adjust the temperature of the gas delivery assembly 220. Additional details of the process chamber can be found in U.S. Patent Application Serial No. 11/063,645, filed on Feb. 22, 2005, which is incorporated herein by reference.

Process chamber 100 is particularly useful for performing a plasma assisted dry etch process that requires heating and cooling the surface of the substrate without breaking the vacuum. In an embodiment, the process chamber 100 can be used to selectively remove one or more oxides on the substrate.

In one example, ammonia (NH ₃₎ and nitrogen trifluoride (NF ₃₎ gas mixture to remove one or more oxides of silicon dry etching process may be performed within the processing chamber 100. It is believed that the process chamber 100 is advantageous for any dry etch process (including annealing processes) that can benefit from the plasma process, in addition to substrate heating and cooling, all in a single process environment.

Referring to FIG. 3, the dry etch process begins by placing substrate 110 into process chamber 100. The substrate is typically placed into the chamber body 112 through the slit valve opening 160 and disposed on the upper surface of the support member 310. The substrate 110 can be clamped to the upper surface of the support member 310. Preferably, the substrate 110 can be clamped to the upper surface of the support member 310 by evacuating the vacuum. Next, if the support member 310 is not yet in the process position, the support member 310 is raised to a process position within the chamber body 112. Preferably, chamber body 112 is heated to a temperature between about 50 ° C to about 80 ° C, such as about 65 ° C. The temperature of the chamber body 112 is maintained by flowing the heat transfer medium through the passage 113.

Substrate 110 is cooled to below about 65 °C, such as between about 15 °C and about 50 °C, by flowing a heat transfer medium or coolant through a passage formed in support assembly 300. In one embodiment, the substrate is maintained at or below room temperature. In another embodiment, the substrate is heated to a temperature between about 22 ° C to about 40 ° C. Typically, to achieve a desired substrate temperature, support member 310 is maintained below about 22 °C. To cool the support member 310, coolant is caused to flow through the fluid passage formed in the support assembly 300. In order to better control the temperature of the support member 310, it is preferred to use a continuously flowing coolant. In one example, the coolant contains about 50 volume percent (vol%) ethylene glycol and 50 volume percent (vol%) water. Other ratios of water and ethylene glycol can be used as long as the substrate can be maintained at the desired temperature.

In order to selectively remove various oxides on the surface of the substrate 110, an etching gas mixture is introduced into the process chamber 100. In one embodiment, ammonia and nitrogen trifluoride gas are then introduced into the process chamber 100 to form an etching gas mixture. The amount of each gas introduced into the chamber is variable and can be adjusted to match, for example, the thickness of the oxide layer to be removed, the geometry of the substrate being cleaned, the volumetric capacity of the plasma, and the chamber body 112. Volume capacity, and the ability to couple to the vacuum system of the chamber body 112.

The ratio of the etching gas mixture can be predetermined to selectively remove various oxides on the surface of the substrate. In an embodiment, the ratio of the plurality of gases in the etching gas mixture can be adjusted to remove various oxides such as thermal oxides, deposited oxides, and/or native oxides. In one embodiment, the molar ratio may be set in the etching gas mixture of ammonia and nitrogen trifluoride (referred to as NH ₃ / NF ₃ mole ratio herein) to remove the native oxide. In one embodiment, the gas is added to provide a gas mixture having a molar ratio of ammonia to nitrogen trifluoride of at least 1:1. NH embodiment, the etching gas mixture In another embodiment of the ₃ / NF ₃ mole ratio based at least about 10, preferably about 15 or more, and more preferably about 20 or greater (e.g., about 30).

The NH ₃ /NF ₃ molar ratio is proportional to the gas flow rate ratio of ammonia to nitrogen trifluoride. In one embodiment, the flow rate of ammonia into the process chamber may be between about 20 sccm and about 300 sccm, preferably between about 40 sccm and about 200 sccm, more preferably between about 60 sccm and about 150 sccm. More preferably, it is between about 75 sccm and about 100 sccm. The flow rate of nitrogen trifluoride flowing into the process chamber may be between about 1 sccm and about 60 sccm, preferably between about 2 sccm and about 50 sccm, more preferably between about 3 sccm and about 25 sccm, and more preferably. It is between about 5 sccm and about 15 sccm.

A purge gas or carrier gas may also be added to the etching gas mixture. Any suitable purge gas/carrier gas can be used, such as argon, helium, hydrogen, nitrogen, or mixtures thereof. Typically, the ammonia and nitrogen trifluoride of the entire etching gas mixture is between about 0.05% and about 20% by volume. The flow rate of the carrier gas stream into the process chamber can be between about 200 sccm and about 5000 sccm, preferably between about 500 sccm and about 4000 sccm, more preferably between about 1000 sccm and about 3000 sccm. In one embodiment, to stabilize the pressure within the chamber body 112, a purge gas or carrier gas is introduced into the chamber body 112 prior to the reaction gas. The operating pressure within the chamber body 112 is variable. Generally, the internal pressure of the chamber body 112 can be between about 500 mTorr and about 30 Torr, preferably between about 1 Torr and about 10 Torr, and more preferably between about 3 Torr and about 6 Torr.

In order to align the plasma of the gas mixture within the spaces 261, 262 and 263 contained in the gas delivery assembly 220, RF power can be applied to the electrode 240. The RF power can be between about 5 watts and about 600 watts, preferably less than about 100 watts (e.g., about 60 watts or less), preferably about 50 watts or less, and more preferably about 40 watts or less. smaller. In an embodiment, lower RF power may be used during the process to ignite the gas mixture and form a clean plasma. The RF power can be between about 5 watts and about 50 watts, preferably between about 15 watts and about 30 watts. In one example, the plasma is produced using RF power of about 30 watts or less. In another example, the plasma is produced using RF power of about 15 watts or less. Typically, the frequency of applied power is very low, such as less than 100 kHz. Preferably, the frequency can be between about 50 kHz and about 90 kHz.

The plasma energy decomposes ammonia and nitrogen trifluoride into reaction species that combine to form a reaction gas such as ammonium fluoride (NH ₄ F) and/or ammonium hydrogen fluoride (NH ₄ F.HF ₂ ). This gas mixture flows through the gas delivery assembly 220 via the holes 225A of the gas distribution plate 225 to react with the surface of the substrate containing an oxide layer, such as a native yttria layer. In one embodiment, a carrier gas is first introduced into the process chamber 100 to produce a plasma of the carrier gas, and then the reactant gases, ammonia, and nitrogen trifluoride are added to the plasma.

Without wishing to be bound by theory, it is believed that the etching gas, ammonium fluoride and/or ammonium hydrogen fluoride react with the surface of the cerium oxide to form ammonium hexafluoroantimonate ((NH ₄ ) ₂ SiF ₆ ), ammonia and water. The ammonia and water of the gas can be removed from the process chamber 100 by a vacuum pump 125. In particular, the volatile gas flows through the holes 135 formed in the liner 133 into the pumping passage 129 before the gas exits the process chamber 100 through the vacuum crucible 131 into the vacuum pump 125. A film containing ammonium hexafluoroantimonate is formed on the surface of the substrate. The reaction mechanism can be summarized as follows:

NF ₃ + _XS NH ₃ →NH ₄ F+NH ₄ F‧HF ₂ +N ₂ 2NH ₄ F+2NH ₄ F‧HF ₂ +SiO ₂ →(NH ₄ ) ₂ SiF ₆ +2H ₂ O+2NH ₃ (NH ₄ ) ₂ SiF ₆ + heat → 2NH ₃ + 2HF + SiF ₄

After the film is formed on the surface of the substrate, the support member 310 can be raised to an annealing position against the heated gas distribution plate 225. The heat radiated from the gas distribution plate 225 can decompose or sublimate the hexafluoroantimonic acid plating film into volatile compounds such as antimony tetrafluoride, ammonia, and hydrogen fluoride. These volatile products are then removed from the process chamber 100 by a vacuum pump 125 as described above. Typically, the film is decomposed and removed from the substrate at a temperature of about 75 ° C or greater, preferably about 100 ° C and greater (e.g., between about 115 ° C to about 200 ° C).

The thermal energy which decomposes the ammonium hexafluoroantimonate film into a volatile component is convection or radiation by the gas distribution plate 225. As described above, the heating member 270 is directly coupled to the distribution plate 225 and the heating member 270 is operated to heat the distribution plate 225 and the components in thermal contact therewith to a temperature between about 75 ° C and about 300 ° C, It is preferably between about 100 ° C and about 200 ° C, more preferably between about 110 ° C and about 150 ° C (eg, about 120 ° C).

This rising change can be achieved in a variety of ways. For example, the lifting mechanism 330 can raise the support member 310 toward the lower surface of the distribution plate 225. During this ascending step, the substrate 110 is secured to the support member 310, such as by vacuum or electrostatic clamping as described above. Alternatively, the substrate 110 can be raised from the support member 310 and placed in close proximity to the heated distribution plate 225 by raising the lift tip 325 through the lift ring 320.

The distance between the upper surface of the substrate 110 having the film thereon and the distribution plate 225 is not critical, but is a result of routine experimentation. Anyone familiar with the art can readily determine the spacing required to evaporate the film quickly and efficiently without damaging the underlying substrate. However, we believe that the spacing between about 0.254 mm (10 mils) and 5.08 mm (200 mils) is effective.

Once the film has been removed from the substrate, the process chamber 100 is purged and evacuated. The treated substrate is then removed from the chamber body 112 by lowering the substrate support 300 to the transfer position, loosening the substrate, and transporting the substrate via the slit valve opening 160.

An embodiment of the invention can be used to uniformly remove multiple oxides during fabrication of shallow trench isolation regions. STI is the primary form of component isolation technology for the sub-0.25 micron process. STI fabrication typically includes trench masking and etching, sidewall oxidation, trench filling, and planarization. 4A-4I are cross-sectional schematic views of a process sequence for forming shallow trench isolation regions in accordance with an embodiment of the present invention.

FIG. 4A illustrates the semiconductor substrate 401 after forming the barrier oxide layer 402 and depositing the nitride layer 403. The substrate 401 may be a tantalum substrate having a <100> crystal orientation and having a diameter of 150 mm (6 inches), 200 mm (8 inches), or 300 mm (12 inches). The barrier oxide layer 402 can be grown on the substrate 401 in a high temperature oxidation furnace. The barrier oxide layer 402 may have a thickness of about 150 . The barrier oxide layer 402 can protect the substrate 401 from contamination during subsequent nitride stripping steps. The nitride layer 403 can be formed in a high temperature low pressure chemical vapor deposition (LPCVD) furnace. The nitride layer 403 is generally a thin film of tantalum nitride (e.g., Si ₃ N ₄ ) formed by the reaction of ammonia and methane chloride gas. Nitride layer 403 is a durable masking material that protects substrate 401 during oxide deposition and as a polishing termination material during subsequent chemical mechanical polishing (CMP).

FIG. 4B illustrates a photoresist layer 404 formed, exposed, and developed on the nitride layer 403. A trench pattern can be formed on the photoresist layer 404. Subsequent nitride etch and oxide etch steps may form trench patterns 405 in nitride layer 403 and barrier layer 402 that expose locations in substrate 401 that are designated as isolation regions.

FIG. 4C illustrates the formation of shallow trenches 406 within substrate 401 using an etching process such as dry plasma etching. The shallow trenches 406 will later be filled with a dielectric material and will serve as an isolation material between the electronic components (eg, metal field effect transistors (MOSFETs) on the substrate) that are built onto the substrate 401.

4D shows a liner oxide layer 407 formed inside the shallow trenches 406. The liner oxide layer 407 is typically grown in a high temperature oxidation furnace. The purpose of the liner oxide layer 407 is to improve the interface between the substrate 401 and the trench oxide to be filled.

4E illustrates a nitride liner 408 formed on the inner liner oxide layer 407 inside the shallow trench 406. A nitride liner 408 can be formed from decane and ammonia in a carrier gas such as nitrogen or argon through a plasma assisted chemical vapor deposition (PECVD) process. The purpose of the nitride liner 408 is to induce stress in the shallow trenches 406 and to avoid mechanical failure caused by stressed oxides.

FIG. 4F shows the trench oxide 409 filled in the shallow trench 406 and the trench pattern 405. The trench oxide 409 is typically formed by a CVD process at a relatively high deposition rate. The trench oxide 409 is overfilled such that the trench oxide 409 is higher than the top surface of the substrate 401.

In order to obtain a flat surface as shown in Fig. 4G, a CMP process can be applied. The CMP process removes excess oxide from the trench oxide 409.

In order to remove the nitride layer 403 and expose the plurality of oxides, the thermal oxide of the barrier layer 402, the deposited oxide of the trench oxide 409, the thermal oxide of the liner oxide layer 407, and the nitride of the nitride liner 408. The oxide can be subjected to a nitride stripping step as shown in Figure 4H.

Typically, an oxide etch step will be performed to make the shallow trench structure available for subsequent processing steps, such as various well implants. Figure 4I shows the STI after the dry etch process. The dry etch process of the present invention can be used to etch various oxides exposed in Figure 4H to achieve a substantially flat top surface on shallow trenches 409 and to avoid undesirable bonding or leakage currents. In an embodiment, a dry etch process can be performed in a process chamber similar to process chamber 100. The substrate 400 can be placed in a process chamber and heated to a temperature of about 100 ° C or less, preferably about 80 ° C or less, and more preferably about 60 ° C or less, such as between about 20 Between ° C and about 60 ° C, preferably between about 25 ° C and about 50 ° C, and more preferably between about 30 ° C and about 40 ° C (eg, about 35 ° C).

In order to remove various oxides on the surface of the substrate 400, an etching gas mixture is introduced into the process chamber 100. In one embodiment, an etching gas mixture comprising ammonia and nitrogen trifluoride gas is introduced into the process chamber. Adjustable to match, for example, the thickness of the oxide layer to be removed, the geometry of the substrate 400, the volumetric capacity of the plasma, the volumetric capacity of the chamber, the capabilities of the vacuum system, and the nature of the different oxides on the substrate 400. Amount and ratio of ammonia and nitrogen trifluoride. A purge gas or a carrier gas may also be added to the etching gas mixture. The plasma of the etching gas mixture is then ignited. The plasma reacts with the oxide to leave a film of ammonium hexafluoroantimonate on the substrate 400.

Then, in order to sublimate the film, the substrate 400 is heated to a temperature of about 100 ° C or greater, such as between about 100 ° C to about 200 ° C, preferably between about 100 ° C and about 150 ° C. More preferably, it is between about 110 ° C and about 125 ° C. The process chamber can then be purged and evacuated, and the substrate 100 is ready for the next steps. In one embodiment, the substrate is at a first temperature between about 20 ° C and about 80 ° C during the etching process, and then the substrate is heated to between about 100 ° C and about 150 ° C during the sublimation process. The second temperature between. In another example, the substrate is at a first temperature between about 22 ° C and about 40 ° C during the etching process, and then the substrate is heated to between about 110 ° C and about 125 ° C during the sublimation process. The second temperature between.

The etching process described herein can be used in various etching steps during fabrication, particularly in the step of removing one or more oxides. For example, multiple etch backs prior to implantation and deposition can use the etching process described herein. In one embodiment, the etching process described herein can be used prior to the epitaxial growth/deposition process, polysilicon deposition process, or deuteration process used to form the germanium containing material.

5A-5H illustrate cross-sectional schematic views of a process sequence for forming electronic components such as MOSFET structure 500, including the dry etch process and process chamber 100 described herein. MOSFET structure 500 can be formed on a semiconductor material such as tantalum or arsenide substrate 525. Substrate 525 is preferably a tantalum substrate having a <100> crystal orientation and a diameter of 150 mm (6 inches), 200 mm (8 inches), or 300 mm (12 inches). Typically, MOSFET structure 500 includes the following combinations: (i) a dielectric layer such as cerium oxide, an organic cerium oxide, a carbon doped cerium oxide, a phosphonium silicate glass (PSG), a borophosphonite glass. (BPSG), tantalum nitride, or a combination thereof; (ii) a semiconductor layer such as doped polysilicon, n-type or p-type doped single crystal germanium; and (iii) a metal layer or a metal telluride layer Electrical contacts and interconnects formed by tungsten, tungsten telluride, titanium, titanium telluride, cobalt telluride, nickel telluride, or combinations thereof.

Referring to Figure 5A, the fabrication of active electronic components begins with the formation of an electrically isolated region structure that electrically isolates the active electronic components from other components. There are several types of electrical isolation region structures, such as field oxide barriers, or shallow trench isolation regions. In this case, shallow trench isolation regions 545A and 545B surround the exposed regions of the electronic active components in which the components are formed and prepared. The STI can include two or more oxides as described in Figures 4A-I. In order to form a thin gate oxide layer 550 having a thickness of about 50 to 300 angstroms, the exposed regions are thermally oxidized. The polysilicon layer is then deposited, patterned, and etched to form a gate electrode 555. To form the insulating dielectric layer 560, the surface of the polysilicon gate electrode 555 can be reoxidized to provide the structure shown in FIG. 5A.

Figure 5B shows source 570A and drain 570B formed by doping a suitable region with appropriate dopant atoms. For example, for p-type substrate 525, an n-type dopant species comprising arsenic or phosphorus is used. Typically, the doping is performed by an ion implanter and may include, for example, phosphorus having a concentration of about 10 ¹³ atoms/cm ² and an energy of about 30 to 80 keV, or a dose of about 1 x 10 ¹⁵ to 1 x 10 ¹⁷ atoms/cm. ² and arsenic with an energy of about 10 to 100 keV. After the implant process, the dopant is introduced into the substrate 525 by heating the substrate, such as in a rapid thermal process (RTP) device. Thereafter, the thin gate oxide layer 550 covering the source 570A and drain 570B regions is stripped through a dry etch process as described above to remove any impurities trapped in the thin gate oxide layer 550 caused by the implant process. Two or more oxides in the shallow trench isolation regions 545A and 545B may also be etched. The etching gas mixture can be adjusted to match the various etch rates required for different oxides.

Referring to FIGS. 5C and 5D, a gas mixture of decane (SiH ₄ ), chlorine (Cl ₂ ), and ammonia (NH ₃ ) is used on the gate electrode 555 and the surface of the substrate 525 by low pressure chemical vapor deposition (LPCVD). A tantalum nitride layer 575 is deposited thereon. As shown in FIG. 5D, in order to form a nitride spacer 580 on the sidewall of the gate electrode 555, a tantalum nitride layer 575 is subsequently etched using a reactive ion etching (RIE) technique. The spacer 580 electrically isolates the germanide layer formed on the top surface of the gate electrode 555 from the other germanide layers deposited on the source 570A and the drain 570B. It should be noted that the electrically isolated sidewall spacers 580 can be fabricated from other materials such as yttria. The ruthenium oxide layer for forming the sidewall spacers 580 is typically deposited by CVD or PECVD from a feed gas of tetraethoxy decane (TEOS) at a temperature of from about 600 ° C to about 1000 ° C. Although shown in the figures to form spacers 580 after implantation and RTP activation, spacers 580 may be formed prior to source/drain implantation and RTP activation.

Referring to Figure 5E, the native yttria layer 585 is typically formed on the exposed ruthenium surface by exposure to the atmosphere before and after the process. In order to improve the alloying reaction and conductivity of the formed metal halide, it is necessary to remove the native contact before forming the conductive metal telluride contacts on the gate electrode 555, the source metal 570A and the drain metal 570B. The yttrium oxide layer 585. The native yttria layer 585 can increase the electrical resistance of the semiconductor material and adversely affect the subsequent deposition of germanium and metallization. Therefore, the native ruthenium oxide layer 585 must be removed using the dry etch process described prior to forming the metal hydride contacts or conductors used to connect the active electronic components. The dry etch process described above can be used to remove the native yttria layer 585 to expose the top surface of source 570A, drain 570B, and gate electrode 555, as shown in FIG. 5F. The oxides in the shallow trench isolation regions 545A and 545B are also exposed to a dry etch process. In order to obtain a uniform removal rate on different surfaces, the dry etching process can be appropriately adjusted, such as a reaction gas ratio.

Thereafter, as shown in FIG. 5G, in order to deposit the metal layer 590, a physical vapor deposition (PVD) or sputtering process is used. Subsequently, in order to form a metal telluride in the region where the metal layer 590 is in contact with the crucible, conventional furnace annealing is used to anneal the metal and germanium layers. Annealing is typically performed in a separate processing system. Thus, a protective cap layer (not shown) can be deposited over the metal 590. The cap layer is typically a nitride material and may comprise a group selected from the group consisting of titanium nitride, tungsten nitride, tantalum nitride, tantalum nitride, tantalum nitride, derivatives thereof, alloys thereof, or combinations thereof. One or more materials. The cap layer can be deposited by any deposition process, preferably a PVD process.

Annealing typically involves heating the MOSFET structure 500 to a temperature between 600 ° C and 800 ° C for about 30 minutes in a nitrogen atmosphere. Alternatively, the metal telluride 595 can be formed using a rapid thermal annealing process that rapidly heats the MOSFET structure 500 to about 1000 ° C for about 30 seconds. Suitable conductive metals include cobalt, titanium, nickel, tungsten, platinum, and any other metal that has low contact resistance and can form a reliable metal halide junction on polycrystalline germanium and single crystal germanium.

The unreacted portion of the metal layer 590 can be removed by wet etching using aqua regia (HCl and HNO ₃ ) which does not attack the metal telluride 595, the spacer 580 or the field oxides 545A, B, thereby removing the metal layer 590. Self-aligned metal telluride 595 is left on pole electrode 555, source 570A, and drain 570B, as shown in FIG. 5H. Thereafter, an insulating cap layer including, for example, yttrium oxide, BPSG or PSG may be deposited on the electrode structure. The insulating cover layer can be deposited by chemical vapor deposition in a CVD chamber, wherein the material from the feed gas is condensed at a low pressure or a pressure, as described, for example, in the commonly assigned U.S. Patent No. 5,500,249. Use it as a reference. The MOSFET structure 500 is then annealed at a glass transition temperature in order to form a smooth, flat surface.

Although the above described process sequence for the formation of MOSFET elements has been described, the dry etch process described herein can also be used to form other semiconductor structures and components that require removal of various oxides. Dry etching processes can also be used prior to deposition of different metal layers including, for example, aluminum, copper, cobalt, nickel, niobium, titanium, palladium, tantalum, boron, tungsten, tantalum, alloys thereof, or combinations thereof.

In an embodiment, the dry etch process described herein in the embodiments can be combined with an aqueous etch process. For example, for an oxide structure having at least two oxides, a dry etch process may be used to selectively remove the first oxide, which completely or partially reduces the first oxide feature relative to the second oxide. The aqueous HF etching process can then be used to remove the second oxide.

In order to provide a better understanding of the foregoing description, the following non-limiting examples are given. While this example may be directed to a particular embodiment, the examples are not to be considered as limiting the invention in any particular respect.

Example:

The substrate is exposed to various etching processes to remove the native oxide layer and form a passivated surface on the substrate. The substrate is then exposed to ambient conditions during a time sequence and a secondary native oxide layer is formed on the passivated surface. The thickness of the secondary native oxide layer is monitored in time series while exposing the substrate to ambient conditions, as depicted in FIG. The various etching processes included Experiments A-E as outlined in the following table.

In Experiment A, substrate A was exposed to an HF wet cleaning solution and process. In Experiments B and C, substrates B and C were exposed to an etching gas mixture having a NH ₃ /NF ₃ molar ratio of about 5 and about 2, respectively, and both exposed to electricity ignited at an RF power of about 30 watts. Pulp. In Experiments D and E, both substrates D and E were exposed to an etching gas mixture having a NH ₃ /NF ₃ molar ratio of about 20, but were respectively exposed to ignition at different RF powers of about 30 watts and 15 watts. Plasma.

For Experiment B-E, argon was also introduced into the process chamber with ammonia and nitrogen trifluoride at a flow rate of about 3500 sccm. The internal pressure of the process chamber was about 3 Torr and the substrate temperature was about 35 °C. To form a film containing ammonium hexafluoroantimonate, the substrate was etched for up to 120 seconds.

During the subsequent annealing process, the spacing between the substrate surface and the showerhead was about 750 mils. The chamber was purged with argon at a flow rate of about 1500 sccm in the chamber, and edge-purified with argon at a flow rate of about 500 sccm. To remove the film by sublimation and/or decomposition while passivating the surface of the substrate, the lid is heated to a temperature of about 120 ° C and the substrate is annealed for up to about 60 seconds. About 50 The raw cerium oxide-containing material is removed from the surface of each substrate.

Once the experimental AE completed the etching process, the substrate AE was withdrawn from the process chamber and placed in an external environment, thereby exposing the substrate to oxygen and water in the air at room temperature (about 22 ° C). After about 5 hours of sequence, substrates A, B, and C each contain greater than about 5 Oxide layer, while substrates D and E each contain less than about 5 The oxide layer. After about 10 hours of time sequence, substrates A, B, and C each contain greater than about 7 Oxide layer, while substrates D and E each contain less than about 6 The oxide layer. Substrates A, B, and C each contain greater than about 8 after about 15 hours, 20 hours, and 25 hours of timing. Oxide layer, while substrates D and E each contain less than about 6 The oxide layer. In addition, after about 30 hours of sequence, substrates A, B, and C each contain about 9 Or a larger oxide layer, while substrates D and E each contain less than about 7 The oxide layer.

The passivated surface formed during Experiments D and E limits further formation of another native oxide on the substrate during a period of between about 5 hours and about 25 hours when the substrate is exposed to the outer boundary conditions of the process chamber. To about 6 Or smaller thickness. In addition, the passivated surface formed during Experiments D and E limits further native oxide on the substrate during a period of between about 15 hours and about 30 hours when the substrate is exposed to the outer boundary conditions of the process chamber. Formation to about 8 Or smaller (preferably about 7 Or smaller, and more preferably about 6 Or smaller) thickness.

All numbers expressing quantities of properties, reaction conditions and the like in the specification and claims are to be understood as an approximation. These approximations are based on the desired properties and measurement errors to be obtained by the present invention, and at least the number of significant digits reported should be considered and interpreted using general rounding techniques. In addition, any of the quantities represented herein, including temperature, pressure, spacing, molar ratio, flow rate, etc., can be further optimized to achieve the desired etch selectivity and performance.

While the foregoing description is directed to embodiments of the present invention, other and additional embodiments of the present invention can be devised without departing from the basic scope thereof.

1. . . Layer

2. . . Shallow ditch

3. . . Source

4. . . Bungee

5. . . Polycrystalline germanium

6. . . Gate oxide layer

7. . . Thermal oxide layer

8. . . Deposited oxide layer

9. . . gap

10. . . Substrate

100. . . Process chamber

110. . . Substrate

112. . . Chamber body

113. . . aisle

125. . . Vacuum pump

127. . . Throttle valve

129. . . Pumping channel

131. . . Vacuum

133. . . Lining

135. . . Hole

140. . . Remote plasma generator

160. . . Slit valve opening

200. . . Cover assembly

210. . . Cover edge

220. . . Gas delivery assembly

225. . . Gas distribution plate

225A. . . Hole

230. . . Distinguishing element

240. . . electrode

250. . . roof

270. . . Heating member

300. . . Support assembly

310. . . Support member

314. . . axis

320. . . Lifting ring

325. . . Lifting tip

330. . . Lifting mechanism

333. . . Folding box

340. . . power supply

400. . . Substrate

401. . . Substrate

402. . . Barrier oxide layer

403. . . Nitride layer

404. . . Photoresist layer

405. . . Ditch pattern

406. . . Shallow ditch

407. . . Lining oxide layer

408. . . Nitride lining

409. . . Ditch oxide

500. . . MOSFET structure

525. . . Substrate

545A. . . Shallow trench isolation zone

545B. . . Shallow trench isolation zone

550. . . Thin gate oxide layer

555. . . Gate electrode

560. . . Insulating dielectric layer

570A. . . Source

570B. . . Bungee

575. . . Tantalum nitride layer

580. . . Clearance wall

585. . . Primary ruthenium oxide layer

590. . . Metal layer

595. . . Metal telluride

The foregoing features and detailed description of the invention may be It is to be understood, however, that the appended claims

Figure 1 shows a partial perspective view of a substrate having a shallow trench isolation region formed therein, as described in one embodiment herein.

Figure 2 shows a partial cross-sectional view of a shallow trench isolation region, as described in an embodiment herein.

Figure 3 is a cross-sectional view showing a process chamber in accordance with an embodiment of the present invention.

4A-4I are schematic cross-sectional views showing a process sequence for forming a shallow trench isolation region in accordance with another embodiment of the present invention.

5A-5H illustrate cross-sectional schematic views of a process sequence for forming isolated electronic components in an STI, as described in one embodiment herein.

Figure 6 shows a graph of oxide growth rates on various passivated substrate surfaces, as described in some embodiments herein.

500. . . MOSFET structure

525. . . Substrate

555. . . Gate electrode

570A. . . Source

570B. . . Bungee

580. . . Clearance wall

595. . . Metal telluride

Claims (20)

A method for removing native oxide from a surface of a substrate, comprising the steps of: placing a substrate in a process chamber, the substrate comprising an oxide layer; adjusting a first temperature of the substrate to about 80 °C or less; generating a cleaning plasma from a gas mixture in the process chamber, wherein the gas mixture comprises ammonia and nitrogen trifluoride and the NH ₃ /NF ₃ molar ratio is about 10 or greater; During the slurry cleaning process, the cleaning plasma is condensed onto the substrate and a film is formed, wherein the film comprises a portion of ammonium hexafluoroantimonate formed from the oxide; and between about 500 mTorr and about 30 Torr. The processing chamber heats the substrate to a second temperature between about 100 ° C and about 200 ° C while operating the pressure while removing the film from the substrate and forming a passivated surface on the substrate. The method of claim 1, wherein the NH ₃ /NF ₃ molar ratio is about 20 or greater. The method of claim 2, wherein the cleaning plasma is produced with an RF power of between about 5 watts and about 50 watts. The method of claim 3, wherein the RF power is between about 15 watts and about 30 watts. The method of claim 1, wherein the gas mixture is formed by combining ammonia having a flow rate of from about 40 sccm to about 200 sccm to nitrogen trifluoride at a flow rate of from about 2 sccm to about 50 sccm. The method of claim 5, wherein the flow rate of ammonia is between about 75 sccm and about 100 sccm, and the flow rate of nitrogen trifluoride is between about 5 sccm and about 15 sccm. The method of claim 1, wherein the first temperature is between about 20 ° C and about 80 ° C. The method of claim 7, wherein the first temperature is between about 22 ° C and about 40 ° C and the second temperature is between about 110 ° C and about 150 ° C. The method of claim 1, further comprising the step of growing an epitaxial layer on the passivated surface of the substrate. The method of claim 1, wherein the passivated surface limits the substrate during a period of between about 5 hours and about 25 hours when the substrate is exposed to external conditions outside the processing chamber. On another The native oxide layer is further formed to a thickness of about 6 Å or less. The method of claim 1, wherein the passivated surface limits the substrate during a period of between about 15 hours and about 30 hours when the substrate is exposed to external conditions outside the processing chamber. The further native oxide layer is further formed to a thickness of about 8 Å or less. A method for removing native oxide from a surface of a substrate, comprising the steps of: placing a substrate in a process chamber, the substrate comprising an oxide layer; adjusting a first temperature of the substrate to less than about 100 ° C; generating a cleaning plasma from a gas mixture in the process chamber, wherein the gas mixture comprises ammonia and nitrogen trifluoride and the NH ₃ /NF ₃ molar ratio is about 20 or greater, and the cleaning plasma Produced with an RF power of between about 5 watts and about 50 watts; during a plasma cleaning process, the substrate is exposed to the cleaning plasma to form a film, wherein the film comprises a portion from the oxide layer Forming ammonium hexafluoroantimonate; and heating the substrate to a second temperature between about 100 ° C and about 200 ° C in the process chamber at an operating pressure of between about 500 mTorr and about 30 Torr, The film is simultaneously removed from the substrate and a passivated surface is formed on the substrate. The method of claim 12, wherein the RF power is between about 15 watts and about 30 watts. The method of claim 12, wherein the gas mixture is formed by combining ammonia having a flow rate of from about 1 sccm to about 10 sccm to nitrogen trifluoride at a flow rate of from about 50 sccm to about 200 sccm. The method of claim 14, wherein the flow rate of ammonia is between about 2 sccm and about 8 sccm, and the flow rate of nitrogen trifluoride is between about 75 sccm and about 150 sccm. The method of claim 12, wherein the first temperature is between about 20 ° C and about 80 ° C. The method of claim 16, wherein the first temperature is between about 22 ° C and about 40 ° C and the second temperature is between about 110 ° C and about 150 ° C. The method of claim 12, further comprising the step of growing an epitaxial layer on the passivated surface of the substrate. The method of claim 12, wherein the passivated surface limits the substrate during a period of between about 5 hours and about 25 hours when the substrate is exposed to external conditions outside the processing chamber. On another A primary oxide is further formed to a thickness of about 6 Å or less. A method for removing native oxide from a surface of a substrate, comprising the steps of: placing a substrate in a process chamber, the substrate comprising an oxide layer; adjusting a first temperature of the substrate to less than about 100 ° C; generating a cleaning plasma from a gas mixture in the process chamber, wherein the gas mixture comprises ammonia and nitrogen trifluoride and the NH ₃ /NF ₃ molar ratio is about 10 or greater, and the cleaning plasma Produced with an RF power of between about 5 watts and about 50 watts; during a plasma cleaning process, the substrate is exposed to the cleaning plasma to form a film, wherein the film comprises a portion from the oxide layer Forming ammonium hexafluoroantimonate; heating the substrate to a second temperature between about 100 ° C and about 200 ° C in the process chamber at an operating pressure of between about 500 mTorr and about 30 Torr, Removing the film from the substrate and forming a passivated surface on the substrate; and growing an epitaxial layer on the passivated surface of the substrate.